1. Field of the Invention
The present invention relates to a stent for dilating an internal lumen.
2. Description of the Related Art
Methods for recovering an indwelling stent are described in Jpn. Pat. Appln. KOKAI Publication No. 10-192411 and U.S. Pat. No. 5,474,563, for example. In these methods, the opposite ends of the stent are axially pulled in opposite directions to contract the stent diametrically inward as the stent is separated from an internal lumen and recovered. Described in European Patent Application Publication No. 423,916 is a method in which a stent is drawn out and recovered with its proximal end side contracted diametrically inward.
In many cases, tumors cause constriction of lumens, especially the lumen of a pancreatic or biliary duct system. If a stent is indwelled in one such lumen for a long period of time, the mucous membrane of the lumen may possibly grow into the stent through its stitches or adhere to the mucous membrane.
In recovering the indwelling stent, therefore, it must be separated from the mucous membrane. In the case where the indwelling stent is of a self-expansion type, it is pressed against the mucous membrane in the lumen, making it difficult to be drawn out for recovery.